Barely a day after an engine blew up on a Southwest 737 jet at 30,000 feet, killing one passenger and hurting seven others, the National Transportation Safety Board has identified the likely cause: metal fatigue that caused one of the engine blades to snap off and puncture the fuselage.
Speaking at a late-night briefing at Philadelphia, where the crippled Flight 1380 made an emergency landing, NTSB Chair Robert Sumwalt said agency experts made a preliminary examination of the engine and found that “there’s evidence of metal fatigue where the blade separated from the hub." He added that a chunk of the engine cowling was discovered some 60 miles away from the airport.
Sumwalt, a longtime commercial pilot, stressed the severity of the situation, saying “we are taking this event extremely seriously. This is very unusual. This should not happen," he said with some understatement.
But while this type of incident is rare, the engine involved is one of the most widely used in commercial aviation—a fact that is causing concern in the industry as well as among the traveling public. The CFM56 engine, made by a joint venture of GE and France’s Safran SA, is used by 300 airlines on approximately 6,700 planes. A jet equipped with one of these engines takes off somewhere in the world about every two minutes.
Following two worrying incidents in 2016—one also involving a Southwest 737-700, the same model in this week’s accident—GE issued a service bulletin in June 2017 advising airlines to inspect the engines. At the time, Southwest said it would step up its schedule of planned maintenance checks on all CFM56 engines. The carrier operates more than 700 Boeing 737 jets of varying model types, 500 of which are the -700 series. United and Delta said today that they will be speeding up checks of similar engines in their fleets.
The big question among industry experts is: Is there a systematic failure in the way the industry and its government regulators inspect and maintain these parts?
“Engines are unbelievably reliable. They’re built with the best materials,” says John Goglia, an aviation safety consultant and former member of the NTSB. “Consider that the last failure (two years ago) was effectively a couple of million of flight hours ago." That’s partly because of improvements in ultrasound and other technology used to do the inspections. “It’s all data-driven now; they get a really good looking-at,” he says.
However, he says, federal investigators will study at whether the schedule for mandatory inspections had slipped. There is precedent. Around ten years ago, the FAA launched a major audit of several airlines, , for not performing required maintenance checks. The revealed a culture of coziness between government inspectors and the airlines they were monitoring.
Another factor to consider is the number of takeoff and landing cycles that a plane and its engines endure. More cycles means more wear and tear. Southwest is known for keeping its planes in the air more hours in the day than other major airlines, and it specializes in frequent service on its bread-and-butter short and medium-length routes.
Industry experts point out that flying is still incredibly safe: It was the first in-flight fatality due to an accident in Southwest’s 47-year history, and it ended a nearly ten-year period of zero passenger fatalities aboard U.S. airlines. Meanwhile, car accidents kills tens of thousands of Americans each year.
But Southwest's calamity comes on the heels of a “60 Minutes” expose of budget airline for alleged failings in its safety and maintenance. We'll find out a lot more about the details of Flight 1380 as the NTSB's work goes on. One thing we know for now is that the industry can't remain complacent.